On Thursday, 18th September 2008, the Animal Emergency Service (AES) treated a patient with tetrodotoxin.
Sheena, a two-year-old Border Collie, had been walking on the banks of the Nerang River when her owner saw her eating something under a tree at about 3pm. Sheena remained a normal dog for the rest of the 40 minute walk, but became unable to coordinate muscular movements, and was confused when she arrived home. She then vomited twice, and in the second vomit there was a small toadfish about 12cm in length. The fish was decomposed and smelt terrible.
Sheena was taken to her local veterinarian who anaesthetised her and washed out her stomach. This was completed about 5pm, but unfortunately Sheena’s breathing rate decreased and she stopped breathing altogether at around 5.30pm. Sheena’s veterinarian continued to ventilate her through the anaesthetic breathing machine.
Sheena was transported to AES about 6pm, using an ambu bag to ventilate her. When she arrived, she was immediately connected to the ventilator at the practice. Controlling Sheena’s breathing artificially by this ventilator, we also placed a tube into a main artery and performed tests on the blood there, to verify that she was receiving the correct oxygen balance.
Intensive monitoring of Sheena’s blood, urine output, and her lung and heart function were all performed throughout the time she was hooked up to the ventilator. A critical care veterinary nurse stayed with Sheena at all times while she was on the ventilator.
The ventilator continued to assist Sheena breathe; regular adjustments were made as she started to take a few breaths by herself, from around 11pm. She was able to come off the ventilator completely at 2am. By the time AES closed at 8am, Sheena was able to walk and was discharged back to her regular veterinary clinic. She was later discharged home that evening, which meant that her hospital stay was about 24 hours in total.
Tetrodotoxin is one of the most potent paralysers that we encounter. The effects are rapidly progressive, but have happily been short lived in the patients we have encountered at AES. Fortunately so far, our patients have always vomited the fish which enables the diagnosis, but I feel the syndrome would be exceedingly difficult to diagnose and give a prognosis for, if the vomiting episode is not witnessed and mentioned to us.
Being an avid fisherman, I have found that toadfish are one of the most common inhabitants of the sheltered waterways around the coast. They are easy to catch and they are often killed by fishermen when caught. I will certainly be questioning owners about exposure to them, in any limp animal presenting to us. The prognosis with short term ventilation is good, so I would recommend 12-24 hours ventilation of any patient with extreme flaccid paralysis of unknown cause, in case tetrodotoxin is the source. The use of an up to date human ventilator has improved the management of many severely ill tick and snake cases as well.
There are many different types of Puffer Fish in Australia – for photographs and more information, click here
Written by Dr Robert Webster